Explanation:

Strait of Dover is the strait at the narrowest part of the English Channel, marking the boundary between the Channel and North Sea, separating Great Britain from continental Europe. The shortest distance across the strait, 33.3 kilometres (20.7 miles; 18.0 nautical miles), is from the South Foreland, northeast of Dover in the English county of Kent, to Cap Gris Nez, a cape near to Calais in the French département of Pas-de-Calais. Between these points lies the most popular route for cross-channel swimmers. The entire strait is within the territorial waters of France and the United Kingdom, but a right of transit passage under the UNCLOS exists allowing unrestricted shipping.